weathering and corrosion testing in the ... - … · 17m-0479 1 weathering and corrosion testing in...
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WEATHERING AND CORROSION TESTING IN THE AUTOMOTIVE INDUSTRY AN OVERVIEW OF TODAYrsquoS REQUIREMENTS Andy Francis Q-Lab Corporation
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Weathering and Corrosion
Weathering
Changes in material properties resulting from exposure to the radiant energy present in sunlight in combination with heat (including temperature cycling) and water in its various states predominately as humidity dew and rain
(Atmospheric) Corrosion
Deterioration and destruction of a material and its vital properties due to electrochemical reactions on the surface of a metal in an atmospheric environment It occurs when the surface is wet by moisture formed due to rain fog and condensation
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Weathering and Corrosion Testing
Weathering Corrosion
Outdoor Accelerated Outdoor Accelerated
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Types of Accelerated Tests
Accelerated Test Type Result Test Time Results compared to
Quality Control Pass fail bull Defined bull Short
Material specification
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Types of Accelerated Tests
Accelerated Test Type Result Test Time Results compared to
Quality Control Pass fail bull Defined bull Short
Material specification
Qualification validation Pass fail
bull Defined bull Medium-long
Reference material or specification
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Types of Accelerated Tests
Accelerated Test Type Result Test Time Results compared to
Quality Control Pass fail bull Defined bull Short
Material specification
Qualification validation Pass fail
bull Defined bull Medium-long
Reference material or specification
Correlative Rank-ordered data bull Open-ended bull Medium
Natural exposure (Benchmark site)
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Types of Accelerated Tests
Accelerated Test Type Result Test Time Results compared to
Quality Control Pass fail bull Defined bull Short
Material specification
Qualification validation Pass fail
bull Defined bull Medium-long
Reference material or specification
Correlative Rank-ordered data bull Open-ended bull Medium
Natural exposure (Benchmark site)
Predictive Service life
Acceleration factor bull Open-ended bull Long
Natural exposure (Service environment)
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Types of Accelerated Tests
Accelerated Test Type Result Test Time Results compared to
Quality Control Pass fail bull Defined bull Short
Material specification
Qualification validation Pass fail
bull Defined bull Medium-long
Reference material or specification
Correlative Rank-ordered data bull Open-ended bull Medium
Natural exposure (Benchmark site)
Predictive Service life
Acceleration factor bull Open-ended bull Long
Natural exposure (Service environment)
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Types of Accelerated Tests
Accelerated Test Type Result Test Time Results compared to
Quality Control Pass fail bull Defined bull Short
Material specification
Qualification validation Pass fail
bull Defined bull Medium-long
Reference material or specification
Correlative Rank-ordered data bull Open-ended bull Medium
Natural exposure (Benchmark site)
Predictive Service life
Acceleration factor bull Open-ended bull Long
Natural exposure (Service environment)
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Types of Accelerated Tests
Accelerated Test Type Result Test Time Results compared to
Quality Control Pass fail bull Defined bull Short
Material specification
Qualification validation Pass fail
bull Defined bull Medium-long
Reference material or specification
Correlative Rank-ordered data bull Open-ended bull Medium
Natural exposure (Benchmark site)
Predictive Service life
Acceleration factor bull Open-ended bull Long
Natural exposure (Service environment)
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Weathering Testing
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Historical Accelerated Weathering Test Standards
bull Several different tester architectures for light delivery ndash Xenon arc ndash Fluorescent UV ndash Others (carbon arc metal halide)
bull Xenon arc light sources reproduce full-spectrum sunlight
bull Hardware-based ldquo10218rdquo lightlight+spray standards were the first widely-used weathering standard tests ndash Almost 100 years old but still in use ndash Common examples ISO 4892-2 ASTM G155 Cycle 1 ISO 113 ndash OK for passfail but not realistic
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SAE J2527 Significant improvement hellip but still a ways to go
bull SAE J2527 (J1960) became the ldquostate of the artrdquo in 1980rsquos bull Research into primary stressors (light water heat) bull Replicated gloss loss seen in Florida exposures
bull This SAE weathering standard was well-researched and a leap forward but did not match real-world weathering factors
bull Light spectra bull Moisture delivery
bull As a result it did not adequately predict Florida outdoor field failures for very durable coatings
bull Chemical change (Photo-oxidation water-based effects) bull Physical change (Cracking Blistering Delaminating)
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Modern Weathering Test Standard Development
bull Outdoor weather data collected to understand real-world weather conditions sunlight heat and water
bull Outdoor weathering test dataset collected to provide basis for correlation
bull Accelerated test cycles developed to match those real-world conditions and degradation mechanisms
bull Variety of materials and failure modes evaluated with accelerated testing to verify validity of test
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Sunlight
Heat
Water
Collect outdoor weather data
Goal Obtain suitable body of field data to develop realistic Accelerated laboratory tests
Approach collect outdoor weather data to better understanding the forces of natural weathering
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bull Include both common field failures amp control materials
bull Use multiple replicates and lots of different materials systems
bull Prepare specimens in a consistent fashion to minimize variability
bull Test according to standards
bull Conduct multiple exposure sets and evaluate frequently
Perform Outdoor Testing
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Deliver Realistic Forces of Weathering Light
A xenon light source with proper optical filters correlates better to outdoor exposure
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High temperature serves primarily to accelerate water uptake Two key guiding principles
1 Do not exceed maximum service temperature
2 Use realistic temperatures to increase correlation
Deliver Realistic Forces of Weathering Heat
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Deliver Realistic Forces of Weathering Water
Rotating Drum Flat Array
Shielded sponge holder
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Develop a cycle that mimics a typical Florida outdoor daily cycle
0 2 4 6 8 10 12 14 16 18 20 22 24
Time (hours)
Light Intensity Panel Water Content
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00
01
02
03
04
05
06
07
08
09
10
0 2 4 6 8 10 12 14 16 18 20 22 24
Time (hours)
Irrad
ianc
e (W
m2 n
m
340n
m)
10218 Not a Good Match with Outdoor Weather
Irradiance Water Spray
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00
01
02
03
04
05
06
07
08
09
10
0 2 4 6 8 10 12 14 16 18 20 22 24
Time (hours)
Irrad
ianc
e (W
m2 n
m
340n
m)
SAE J2527 Not a Good Match with Outdoor Weather
Irradiance Water Spray
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Develop a cycle that mimics a typical Florida outdoors daily cycle
0 2 4 6 8 10 12 14 16 18 20 22 24
Time (hours)
Light Intensity Panel Water Content
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ASTM D7869 Reproduces Natural Weather Cycles
Irradiance Water Spray
Deep Water Penetration
Adhesion Blistering Diffusion
No spray during light steps
Avoids unrealistic failures
Cyclic Stresses (cracking) Surface Erosion (gloss)